Polycarbonate is widely used as a raw material in many different manufacturing sectors. It is believed that the demand for polycarbonate will increase significantly in the coming years and as such, improvements in the polymerization process are currently being developed.
Several processes for the production of polycarbonate are known. For instance, the reaction of phosgene with 2,2-bis(4-hydroxyphenyl)propane, also referred to as bisphenol A under phase transfer conditions. This process has the inherent drawbacks of employing phosgene and of creating chloride containing waste streams.
A different process that does not require the use of phosgene is based on the transesterification of bisphenol A with a dialkyl carbonate or a diaryl carbonate. The dialkyl carbonate has the disadvantage that in the transesterification with bisphenol A, it is not reactive enough to produce polymeric polycarbonate.
The use of a diaryl carbonate, for example diphenyl carbonate (DPC), has the advantage that it is reactive enough to form polymeric polycarbonate. Furthermore, phenol is liberated in the reaction of the diphenyl carbonate with bisphenol A to form polycarbonate. This phenol can be recycled and used in the production of, for example, bisphenol A or diphenyl carbonate that can be used as main raw material in the polymerization.
Due to the increasing demands on polycarbonate production, the process for production of polycarbonate leaves ample room for improvement, in particular in view of the way the raw materials are introduced.